Visible image radio responsive device



Nov. 28, 1950 E. G- LINDER VISIBLE IMAGE RADIO RESPONSIVE DEVICE Filed March 51, 1944 Patented Nov. 28, 1950 VISIBLE IMAGE RADIO RESPONSIVE DEVICE Ernest G. Linder, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application March 31, 1944, Serial No. 528,929

13 Claims. 1

This invention relates to radio frequency field responsive devices and more particularly to a device which includes a plurality of resonators, especially aperture resonators, arranged to form a mosaic in which a radio frequency field is converted into a visible image.

The prior art, as typified b U. S. Patents 2,083,292 and 2,155,471, granted to Aloysius J. Cawley, has disclosed means for making visible radio frequency fields or images. These images may be formed by focusing radio waves reflected from an object. The focused radio frequency image is applied to radio circuits which are connected to a plurality of spark balls disposed in a gaseous medium. The prior art devices are very complicated, diflicult to construct and are not adapted to waves of I centimeter or millimeter length. Moreover, the prior devices are relatively insensitive and are, therefore, useful in viewing only the strongest radio frequency fields so that the effective range is limited.

One of the objects of the present invention is to provide an improved radio frequency field responsive device. Another object is to provide an improved device for establishing visible images of radio frequency fields. Another object is to provide an improved device in which a mosaic of aperture resonators is formed so that each resonator includes a dis-charge gap. An additional object is to provide an improved radio frequency field responsive device in which deleterious couplings between adjacent resonant elements are minimized. A still further object is to provide an improved radio frequency field responsive device in which the number of resonators per unit of effective area of the mosaic is greated than in a plane mosaic.

The invention will be described by referring to the accompanying drawings in which Figure 1 is a perspective view of one embodiment of the invention; Figures 2, 3 and 4 are elevational views of modified forms of aperture resonator mosaics; Figure 5 is a perspective view of a folded aperture resonator mosaic; Figures 6 and '7 are elevational views of aperture resonator mosaics in which coupling between adjacent resonators is minimized; Figure 8 is a schematic diagram illustrating a reflector and a screen which may be included in the device; and Figure 9 is an elevational view of a single row of resonators disposed in a suitable envelope.

Referring to Figure 1, a mosaic i is included within an evacuated envelope 3, the envelope is made of a material including at least one transparent face. T e e v l p ,m y be made of glass,

but preferably of a low loss material such as mica, quartz or the like so that the optical image formed on the mosaic may be viewed from the front or rear. The mosaic is preferably formed by a plurality of symmetrically arranged aperture resonators 5. The mosaic may be a conductor which is apertured to form the aperture resonators 5. Each of the aperture resonators is provided with a discharge gap 1, to which reference will be hereinafter made. The mosaic I may be mounted within the envelope 3 in any conventional manner. An annular electrode 9 may be included within the evelope and spaced from the mosaic so that ionization may be established by means of conductors I! and [3, which are respectively connected to the mosaic and to the annular electrode. The ionizing or biasing potentials may be applied by means of a transformer l5 which is connected to a source (not shown) of varying potential to maintain ions within the device and thus lower the breakdown potential across the gaps. The ionizing potential may include a steady bias provided by a battery H. A rarified gaseous medium such as neon, neon+1% argon, or any inert gas having low ionization potential and maximum luminescence, is preferably included in the evacuated envelope so that the potentials across the resonator discharge gaps readily ionize the gas.

The nature of the aperture resonators may be ascertained from Figures 2 and 3. In the case of Fig. 2, the aperture resonators 5 include the region bounded by the two circles which are interconnected byv the discharge gap 1. The apertures may be formed by piercing a conductive plate H! or the plate may be formed by depositing a conductive film on an insulator such as glass. If a high degree of illumination is desired, the discharge gap is preferably made long or blunt, as shown in Fig. 2. If, however, high radio sensitivity is desired, the discharge gap should be sharply defined, as illustrated by the needlelike points 2! of Fig. 3. In either case the aperture resonators are each made responsive to the frequency of the field to be made visible.

The characteristics of aperture resonators are such that:

21rx/LC where L is the inductance of the two loops represented by the edges of the circular sections, and C is the capacitance of the parallel plate center section of the aperture resonator. A typical example for resonance at 1.25 cm. utilizes a .004

inch copper sheet mosaic wherein the circular apertures have a diameter of .080 inch, are separated by a center capacitive section .010 inch long, and the spacing between the center section walls is .005 inch.

The amount of resolution which may be obtained is dependent upon the number of aperture resonators per unit area of the mosaic. It is, therefore, desirable to use waves of centimeter or millimeter length so that a large number of resonators may be formed per unit area of the mosaic. If the mosaic is folded, as shown in Fig. 5, it is possible to increase the number of resonators per unit of effective area. Another type of mosaic may be formed, as shown in Fig. 4, in which the aperture resonators 5 are bounded b wires or conductive elements. In this case the discharge gap 23'is formed by a pair of the conductors.

In the mosaic arrangement of Fig. 1, coupling exists between the adjacent aperture resonators. The coupling tends to broaden the response of the device, to decrease the resolution and to decrease the sensitivity of the device. In some arrangements it may be desirable to minimize the coupling by the arrangements illustrated in Figs. 6 and '7. In Fig. 6 the coupling between the aperture resonators of adjacent rows has been minimized by the arrangement of the adjacent apertures. For example, if the magnetic field of aperture resonators is represented as going into the plane of the paper in the case of the plus marks and is represented as coming out of the plane of the paper by the dots, it will be seen that the resonator 25 in the upper row is decoupled with respect to the resonator 2? in the lower row because the interlinking magnetic fields will neutralize. In the arrangement of Fig. 7 the coupling between the adjacent resonators of the columns also is minimized. For example, the resonators 29 in the first column are arranged so that the coupling to the resonators 3| in the second column is minimized. While the coupling has been minimized in the devices of Figs. 6 and 7 by arranging the spacing and the instantaneous polarities of the resonant currents so that the currents in adjacent devices neutralize or tend to neutralize, as is well known to those skilled in the art, no attempt has been made to minimize the coupling in the adjacent resonators of Figs. 2, 3, 4, and 5'. The resonators of these devices have been arranged in a symmetrical manner without the benefit of the spacing of the resonators of Figs. 6 and '7.

The diiference in polarit between the devices of Figures 6 and '7 is due to a different mode of oscillation. In a system of a multiplicity of coupled circuits various modes may be excited by arying the frequency of the driving electric The sensitivity of the device may be further increased by providing a reflector R which is arranged an odd integral number of quarter wave lengths behind the mosaic 5, as shown in Fig. 8. The sensitivity may be further increased by disposing a director S an odd integral number of quarter wave lengths in front of the mosaic 5. It should be understood that the mosaic should be disposed almost normal to the direction of propagation of the radio-frequency fields and that the plane of polarization of the aperture resonators should correspond to the plane of polarization of the radio frequency field. As shown in Fig. 9 the mosaic may be arranged as a single row of aperture resonators 5. The resonators are formed by piercing a metal strip which is inserted within a glass enevelope 3. The envelope preferably includes an inert gas as described previously in connection with Figure 1.

The mosaic itself or the reflector or the front of the envelope may be coated with a fluorescent material to increase the light output. The term mosaic, as used throughout the specification and claims, includes any desired geometrical pattern of resonator elements from single rows or single columns to multiple arrangements of suitably disposed resonators.

Thus, the invention has been described as an improved radio frequency field responsive device in which a mosaic of aperture resonators is disposed within a transparent gas filled envelope. Arrangements have been disclosed for minimizing the coupling between adjacent aperture resonators and for increasing the effective area, as well as the sensitivity of the mosaic.

I claim as my invention:

l. A radio frequency field responsive device in cluding an envelope having a rarified gaseous medium therein and a mosaic located within said envelope, said mosaic comprising a plurality of aperture resonators each resonant to the frequency of said field and each having oppositely disposed boundary portions mutually more close- 1y spaced than other portions thereof and providing discharge gaps.

2. A device according to claim 1 wherein said envelope includes a transparent face for viewing said mosaic.

3. A device according to claim 1 including additional means disposed within said envelope for ionizing said gas.

4. A device according to claim 1 including a reflector disposed effectively an odd integral number of quarter wave lengths of said field behind said mosaic.

5. A radio frequency field responsive device including an envelope having a rarified gaseous medium therein and a transparent face, and a conductive member disposed within said envelope and having. rows and columns of aperture resonators each resonant to the frequency of said field and each aperturev including a discharge gap, adjacent ones of said aperture resonators having opposing magnetic fields to minimize magnetic coupling therebetween.

6. A radio frequency field responsive device including an evacuated envelope, and a mosaic located within said envelope, said mosaic including a plurality of adjacently disposed aperture resonators. including discharge gaps and being re,- sponsive to the frequency of said field. andv being folded whereby the number of resonators per unit of eifective area of the mosaic isgreater than in a plane mosaic.

'7. A radio frequency field responsive device including an evacuated envelope having a transparent face, and a conductive member disposed within said envelope and viewable through said face, said member including a plurality of aperture resonators arranged to form a mosaic including discharge gaps forming a part of said resonators and having an actual area greater than the projected area whereby the number of resonators per unitof effective area of the mosaic is greater than in a plane mosaic.

8. A device according to claim '7 including means disposed within said envelope for ionizing said gas.

9. A device according to claim 7 including a reflector disposed effectively an odd integral number of quarter wave lengths of said field behind said mosaic.

10. A radio frequency field responsive device including an evacuated envelope, and a mosaic disposed within said envelope said mosaic including a plurality of aperture resonators each resonant to the frequency of said field and each including a blunt discharge gap.

11. A radio frequency field responsive device including an evacuated envelope, and a mosaic disposed within said envelope said mosaic including a plurality of aperture resonators each resonant to the frequency of said field and each including a sharply defined discharge gap.

12. A radio frequency field responsive device including an evacuated'transparent envelope, a mosaic located within said envelope, said mosaic including a plurality of aperture resonators responsive to the frequency of said field and including discharge gaps, and a fluorescent coating disposed in operative relation to said mosaic.

13. A radio frequency field responsive device including an evacuated envelope having a transparent face, and a conductive member disposed within said envelope and viewable through said face, said member including a plurality of aperture resonators araneed to form a mosaic including discharge gaps forming a part of said resonators and having an actual area greater than the projected area whereby the number of resonators per unit of effective area of the mosaic is greater than in a plane mosaic.

ERNEST G. LINDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 625,823 Zickler May 30, 1899 966,204 Hewitt Aug. 2, 1910 1,819,104 Machlett Aug. 18, 1931 2,015,885 Dallenbach Oct. 1, 1935 2,031,884 Gray Feb. 25, 1936 2,083,292 Cawley June 7, 1937 2,120,765 Orvin June 14, 1938 2,155,471 Cawley Apr. 5, 1939 2,211,843 Bouwers Aug. 20, 1940 2,295,680 Mouromtsefi Sept. 15, 1942 2,421,790 Korman June 10, 1947 

